Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W74/00—Wireless channel access
  • H04W74/08—Non-scheduled access, e.g. ALOHA
  • H04W74/0808—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA]
  • H04W74/0816—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA] with collision avoidance
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/0006—Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L5/00—Arrangements affording multiple use of the transmission path
  • H04L5/003—Arrangements for allocating sub-channels of the transmission path
  • H04L5/0032—Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L5/00—Arrangements affording multiple use of the transmission path
  • H04L5/003—Arrangements for allocating sub-channels of the transmission path
  • H04L5/0058—Allocation criteria
  • H04L5/0064—Rate requirement of the data, e.g. scalable bandwidth, data priority
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L5/00—Arrangements affording multiple use of the transmission path
  • H04L5/003—Arrangements for allocating sub-channels of the transmission path
  • H04L5/0078—Timing of allocation
  • H04L5/0082—Timing of allocation at predetermined intervals
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L5/00—Arrangements affording multiple use of the transmission path
  • H04L5/0001—Arrangements for dividing the transmission path
  • H04L5/0003—Two-dimensional division
  • H04L5/0005—Time-frequency
  • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
  • H04L5/001—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT the frequencies being arranged in component carriers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
  • H04W16/14—Spectrum sharing arrangements between different networks
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/20—Control channels or signalling for resource management
  • H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W74/00—Wireless channel access
  • H04W74/002—Transmission of channel access control information
  • H04W74/006—Transmission of channel access control information in the downlink, i.e. towards the terminal
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W74/00—Wireless channel access
  • H04W74/08—Non-scheduled access, e.g. ALOHA
  • H04W74/0833—Random access procedures, e.g. with 4-step access

Definitions

• Various example embodiments relate to communications within unlicensed spectrum.
• the unlicensed spectrum provides an opportunity to increase the bandwidth available for signals to be transmitted. However, as this bandwidth is shared with other devices some scanning of the channel may be needed prior to transmission to reduce interference. Furthermore, there maybe rules regarding how often a device can scan a channel to allow the spectrum to be fairly shared and these issues can lead to increased latency.
• the unlicensed band is divided into sub-bands or channels each covering a certain frequency band and scanning procedures such as listen before talk involves the sensing of these channels to determine whether they are available prior to transmitting a signal.
• scanning procedures such as listen before talk involves the sensing of these channels to determine whether they are available prior to transmitting a signal.
• a channel is available the channel may be acquired by the device for a channel occupancy time COT. During this time signals may be transmitted and other devices are deterred from using the channel.
• Devices are increasingly being able to transmit and receive on multiple channels. This ability may be used in conjunction with data duplication on different sub-channels to increase the reliability of transmissions.
• it is required for the transmitter to scan each channel separately prior to transmission. Where the channels are close in the frequency band a channel cannot be scanned while a transmission is occurring. Thus, in some cases it may be desirable to wait for multiple channels to be available prior to transmitting, however, if one of the channels is blocked then this can significantly increase latency. It would be desirable to provide a system for communicating in the unlicensed spectrum in a manner which is both efficient and has some control on latency.
• an apparatus comprising means configured to: initiate scanning of a plurality of channels in unlicensed spectrum to determine whether said plurality of channels are available; determine a transmitting opportunity at which said apparatus is able to transmit a signal on at least one channel sensed to be available during said scanning; estimate at least one further transmitting opportunity when it is estimated that said apparatus may be able to transmit a signal on at least one other channel in unlicensed spectrum; and ascertain whether a delay between said transmitting opportunity and said at least one further transmitting opportunity lies within a current deferral allowance for said apparatus; and where not control transmission of a signal on said at least one available channel; and where so wait for one of said at least one further transmitting opportunities that lie within said current deferral allowance before controlling transmission of at least one signal on said at least one available channel.
• Embodiments seek to address the competing issues, each of which may potentially increase latency, that arise when seeking to transmit signals on different channels of the unlicensed spectrum.
• a first signal is transmitted at a first transmitting opportunity when a channel is sensed as being available, scanning to determine the availability of other channels during the transmission period is impeded.
• the apparatus waits before transmitting the first signal for one or more further channels to become available the apparatus risks an undue delay before any signal is transmitted if a further channel does not become available for a while.
• the apparatus has a deferral allowance which is a delay period in transmitting the signal that may have been set to be at a level that is deemed to be acceptable for certain required latency. This may be set as a time period or as a counter value, the counter value indicating a number of transmission opportunities for example.
• the apparatus is configured to estimate whether a further channel is likely to become available or it is possible that it may do so at a future transmission opportunity within the deferral allowance. If the apparatus estimates this to be the case, then the apparatus delays transmission until a subsequent transmission opportunity where it then makes the same assessment.
• channel denotes a frequency band in unlicensed spectrum that is used for the transmission of signals to other devices, the scanning procedure determining the availability of this frequency band. It may in the description of embodiments on occasion be termed a sub-channel, link or sub band.
• said means is configured to estimate a time of said at least one further transmitting opportunity for said at least one channel from at least one of: a determined status of said channel and a backoff time associated with said channel, said backoff time being a minimum time delay before a transmitting opportunity can occur if said channel is currently and remains idle.
• the apparatus may determine whether it is likely that there will be a transmitting opportunity within the deferral allowance from a number of factors, and in some cases it may determine this from the determined status of the channel, that is whether it is available or idle for example and/or from a backoff time associated with the channel.
• the backoff time is a minimum time delay before a transmitting opportunity can occur if a channel is currently and remains idle.
• said determined status of said channel comprises one of: a sensed status sensed during a previous measurement time period, or an estimated status based on said sensed status and historical availability of said channel.
• the status of the channel is important and its current status may not be known, but it may be determined either from the status sensed at a previous measurement time period or from a historical availability of the channel from which its likely status may be estimated, or from a combination of a previous measurement and historical availability.
• said previous measurement time period comprises a measurement period immediately preceding a most recent transmitting opportunity
• said means is configured to determine if any of said at least one other of said multiple channels is available at one of said at least one further transmitting opportunities and where so said means is configured to control transmitting said at least one signal on said at least one available channel and at least one further signal on said at least one other available channel at said one of said at least one further transmitting opportunities.
• signals may be transmitted both on the first channel that was sensed to be available and on any other channels that are sensed to be available at the next transmitting opportunity. In this way, multiple channels are used for transmitting one or more signals and the reliability and/ or bandwidth of transmission is increased.
• said means is configured to determine whether all of said at least one other of said multiple channels are busy and where so to control transmission of said at least one signal on said at least one available channel at a next transmitting opportunity.
• the apparatus may then make the decision to transmit the signal on the available channel. In this way, there is not unnecessary delay in transmitting the signal while waiting for channels that will not become available.
• said at least one signal and said at least one further signal are a same signal, said apparatus being configured to transmit duplicate signals on multiple channels.
• Embodiments may be particularly effective at transmitting duplicate signals on different channels and thereby improving the reliability of a transmission. Where duplicate signals are to be transmitted then allowing them to be transmitted simultaneously on multiple channels is a very effective way of increasing reliability. If one signal is transmitted on one channel then there is a delay before a subsequent channel can be scanned and latency is increased or where the signal is not duplicated reliability is decreased. Embodiments increase the chances of signals being able to be transmitted simultaneously on multiple channels while managing the increase in latency that a blocked channel might introduce.
• said apparatus comprises a user equipment, while in other embodiments, said apparatus comprises a gNB.
• a gNB which corresponds to a base station in 5G may use this technique to transmit signals to one or more devices such as user equipment.
• said one or more signals comprise uplink signals. This may be the case for example where the apparatus is a user equipment.
• the deferral allowance may be set centrally by the network and the apparatus may be configured to receive an indication of the deferral allowance from a network node and to set the deferral allowance accordingly.
• the network node may transmit signals indicating the deferral allowance that is to be used. In some embodiments the network node may also transmit further signals indicating that data duplication is to be used, and that a certain listen before talk scanning procedure is to be used.
• said one or more signals comprise downlink signals which may be the case where apparatus is a gNB.
• the means comprise: at least one processor; and at least one memory including computer program code, said at least one memory and computer program code being configured to, with said at least one processor, cause the performance of the apparatus.
• said apparatus further comprises means for transmitting and receiving signals, and means for scanning channels in unlicensed spectrum
• a method comprising: scanning a plurality of channels in unlicensed spectrum to determine whether said plurality of channels are available; in response to determining at least one of said plurality of channels is available determining a transmitting opportunity at which said apparatus is able to transmit at least one signal on said at least one available channel; estimating at least one delay between said transmitting opportunity and at least one further transmitting opportunity at which it is estimated that said apparatus may be able to transmit a signal on at least one other of said plurality of channels; and determining whether any of said at least one delays lie within a current deferral allowance and where not transmitting said at least one signal on said at least one available channel; and. where so delaying transmitting said at least one signal on said at last one available channel until a further transmitting opportunity within said current deferral allowance.
• said step of estimating said at least one delay comprises estimating a time of said at least one further transmitting opportunity for said at least one channel from at least one of: a determined status of said channel and a backoff time associated with said channel, said backoff time being a minimum time delay before a transmitting opportunity can occur if said channel is currently and remains idle a determined status of said channel.
• said determined status of said channel comprises one of: a sensed status sensed during a previous measurement time period, or an estimated status based on said sensed status and historical availability of said channel.
• said method further comprises determining if any of said at least one other of said plurality of channels is available at one of said at least one further transmitting opportunities and where so controlling said transmitting means to transmit said at least one signal on said at least one available channel and said at least one further signal on said at least one other available channel at said further transmitting opportunity.
• said method comprises determining whether all of said at least one other of said plurality of channels are busy and where so controlling said transmitting means to transmit said at least one signal on said at least one available channel at a next transmitting opportunity.
• said at least one signal and said at least one further signal are a same signal, said method transmitting duplicate signals on multiple channels where multiple channels are available.
• a computer program comprising computer readable instructions which when executed by a processor on an apparatus are operable to control said apparatus to perform a method according to a second aspect.
• an apparatus comprising: scanning circuitry configured to scan multiple channels in unlicensed spectrum to determine whether said channels are available; a transmitter for transmitting one or more signals on one or more of said multiple channels; and control circuitry for controlling transmission of said one or more signals, said control circuitry being configured to initiate said scanning circuitry to scan a plurality of said multiple channels to determine whether said plurality of channels are available; to determine a transmitting opportunity at which said apparatus is able to transmit a signal on at least one channel sensed to be available by said scanning circuitiy; to estimate at least one further transmitting opportunity when it is estimated that said apparatus may be able to transmit a signal on at least one other of said multiple channels; and to ascertain whether a delay between said transmitting opportunity and said at least one further transmitting opportunity lies within a deferral allowance for said apparatus ; and where not to control said transmitter to transmit a signal on said at least one available channel; and where so to wait for one of said at least one further transmitting opportunities that lie within said
• FIG. 1 illustrates examples of transmitting duplicate signals on two sub-channels where self deferral is not used, with and without interference, type Ai LBT procedure without self deferral;
• Fig. 2 illustrates examples of transmitting duplicate signals on two sub-channels where self deferral is used, with and without interference, type At LBT procedure with self deferral;
• Fig. 3 illustrates examples of transmitting duplicate signals on two sub-channels with and without interference, type A2 LBT procedure
• Fig. 4 shows a flow diagram illustrating steps in a method according to an example embodiment
• Fig. 5 illustrates an example of transmitting duplicate signals on two sub-channels using a method according to an embodiment with and without interference on one of the sub-channels
• Fig. 6 schematically shows an apparatus according to an embodiment.
• Increasingly devices are able to transmit and receive on more than one channel and this ability may be used to improve the spectral efficiency and/ or increase the reliability of transmissions, by for example transmitting duplicate data on more than one channel.
• signals are transmitted in unlicensed spectrum as this bandwidth is shared with other devices some scanning of the channel may be required prior to any transmission to determine if a channel is available.
• a device will be impeded from scanning one of the channels while transmitting on the other.
• Type A There are different schemes supported for DL/UL channel access for multi-channel transmission denoted Type A and Type B.
• the transmitter performs cat4 LBT independently on multiple sub-channels. Upon successful LBT on a first sub-channel, the transmitter can either transmit on first sub-channel only or defer transmission until LBT is successful on the second, third, etc. sub-channels. In the latter case, the transmitter performs one shot-LBT again on the first sub-channel prior to transmission.
• Type At LBT counter independently determined for each carrier ⁇
• Type A2 LBT counter is determined for the carrier that has the largest value of the maximum congestion window. Then the LBT counter for all other carriers is set equal to this value (so that LBT counter is initialized to exact the same value on all carriers).
• the transmitter performs cat4 LBT on one first primary sub-channel (selected by the transmitter at most once every second), or uniformly randomly choosing from the set of carriers before each transmission on multiple carriers.
• the transmitter Upon successful LBT on the first primary sub-channel, the transmitter performs one shot- LBT on second, third etc. sub-channels.
• a UE With NR-U UL CG (new radio unlicensed uplink configured grant) framework, a UE can be allocated with semi-persistent UL transmission opportunities that can occur as often as every second OFDM (orthogonal frequency division multiplexing) symbol. Assuming SCS (sub carrier spacing) of 6o kHz, this may correspond to a transmission opportunity every -35 ps.
• OFDM orthogonal frequency division multiplexing
• the transmitter while transmitting on one sub channel, the transmitter can neither perform LBT nor initiate transmission on other sub-channels. So, starting the transmission on the sub-channel that first experiences successful LBT will prevent transmission on other sub-channels during the channel occupancy time.
• a transmitter e.g. a UE
• URLLC ultra reliable low latency communication
• URLLC ultra reliable low latency communication
• This may introduce inefficiencies (e.g. only one subchannel used at a time) that may in the long term negatively impact the latency performance, or defer transmission until all sub-channels are available for transmission. This can obviously impact the latency performance if at least one of the sub-channels experiences LBT blockage. It is also possible that all the sub-channels become busy while self-deferring, causing even more severe problems on the latency.
• a UE is allocated simultaneous UL configured grant transmissions on multiple sub-channels (with repetition/duplication configured in frequency domain):
• Type B multi-carrier channel access the transmitter selects one primaiy sub- channel where it performs cat4 LBT.
• the transmitter can perform cat2 LBT on other sub-channels only after the cat4 LBT is successful on the primaiy sub-channel.
• the primary sub-channel can be selected at most once every one second, or before each transmission based on a random selection. This option is not suitable for the transmission of data with low latency requirements as LBT blockage on the primary sub-channel will block transmission on all sub-channels.
• a UE using Type A LBT may be able to initiate transmission on one sub-channel (#i) while LBT on another sub-channel (#2) is still ongoing. If transmission is initiated in sub-channel #1, then the UE needs to stop LBT on sub-channel #2. In this way, the UE reduces latency but may effectively only transmit on one sub-channel at a time. Where data duplication is being used, besides reducing the reliability of transmission (by transmitting on one sub-channel only), this option may require complicated mechanisms to perform cancelation of duplicates on the sub-channel with no transmission, otherwise the latency may effectively be increased due to (1) transmissions only happening on one sub-channel at a time and (2) unnecessary time- domain multiplexing of data duplicates.
• cat 2 LBT is LBT without random back off. This is a fast LBT which usually has a listening period of 25 microseconds at 5GHz for example and may be used in multi-channel access.
• Cat 4 LBT is LBT with random back off with variable sizes contention window. The contention window length depends on the channel access priority class.
• Fig. 1 shows example of Type At (without self-deferral) multi-carrier access procedure for the transmission of URLLC data using duplication in case interference is experienced on one of the carriers (A), as well as without any interference (B).
• the transmitter (UE) is allocated UL CG transmission on two channels/carriers.
• UL CG resources are allocated with a periodicity of ⁇ 35 Lis (corresponding to ca. 4 CCA slots of 9 ps).
• the example illustrates how, independently of whether the sub-channel #2 is idle or busy, the transmitter (UE) always ends up transmitting only on sub-channel #1 (with the drawbacks highlighted above) as the other sub channel is not available at the same time due to differences in the LBT counters and there is no self deferral to allow the UE to wait for a subsequent channel to be available.
• Type Ai LBT the transmitter could also perform self-deferral and wait until cat4 LBT is successful on other channels.
• this option presents similar drawbacks as Type B channel access described above in case one of the sub-channels is blocked by interference. This scenario is illustrated in Fig. 2 A.
• Fig. 2 Example of Type Ai (with self-deferral) multi-carrier access procedure for the transmission of URLLC (ultra reliable low latency communication) data using duplication in case interference is experienced on one of the carriers (A), as well as without any interference (B).
• the two devices always transmit on the two channels at the same time.
• the latency that this imposes is indicated by the length of the self deferral time and where one of the channels is busy can introduce significant latency.
• the LBT counter does not decrement during the busy period and for 4 CCA slots afterwards and thus, there is a significant delay for the two channels to be available.
• a cat 2 LBT is performed after self deferral to confirm that channel #1 is still available.
• Another option illustrated in Fig. 3 is to set the LBT counter on different sub channels to the same value based on the sub-channel with highest value of the maximum contention window.
• An advantage of this option is that, in the absence of interference on both subchannels, the independent LBT procedures on multiple sub channels are synchronized and should be successful at the same time (thus avoiding transmitting on single sub-channel where other sub-channels are also free from interference). Still, in the presence of interference on one of the sub-channels, transmission on the sub-channel with no interference may be unnecessarily delayed as the LBT counter is determined based on the sub-channel with largest value of the maximum contention window.
• a of Fig.3 interference is experienced on one of the carriers (A) and as in this example there is no self deferral, transmission occurs on sub channel #1 and not on scb channel #2. While transmission occurs on sub channel #1 no scanning can occur on sub channel #2 so this transmission is further delayed.
• B no interference occurs and the device transmits on both sub channels when the LBT procedure is complete. The LBT procedure takes the same time on both sub channels as the LBT counter has been set to the same value.
• embodiments provide a system where a node on sensing one channel to be available will make an informed decision as to whether to transmit on that channel sooner, or to delay and wait for a further channel to be available in order to be able to transmit on more than one channel together.
• the decision will be informed by an assessment of when it is expected that one of the other channels will become available and whether that is within a certain set deferral time or not. Where it is then the node will wait and perhaps assess again later. If at any point the node determines that it is unlikely that any other channel will become available within the set deferral time, then it will choose to transmit on the available channel at the next available transmitting opportunity. In this way blocking of a channel should be avoided as if any blocking is detected or estimated to be likely then self deferral will be cancelled.
• Embodiments propose a novel multi-carrier LBT (listen before talk) mechanism for URLLC (Ultra Reliable Low Latency Communication) data transmission over unlicensed spectrum with sub-ims latency requirements.
• LBT listen before talk
• URLLC Ultra Reliable Low Latency Communication
• the UE is allocated with a set of UL CG (uplink configured grant) that is uplink transmission opportunities that share the same time domain configuration.
• the UE is also provided with a packet delay budget (or deferral allowance) for the specific set of UL CG transmissions.
• the packet delay budget could be configured for the logical channel (LCH) or LCH group which is mapped to the corresponding set of UL CG transmissions.
• the packet delay budget provides the maximum time that the UE is allowed to defer transmission of a signal.
• the packet delay budget is configured as the maximum number of UL CG transmission occasions for which a UE can defer data transmission on a sub-channel following a successful LBT.
• the decision as to whether to perform self-deferral may be taken at each UL transmission opportunity depending on (1) the packet delay budget, (2) the value of the LBT counter in other carriers, and (3) the channels status (idle/busy) of other carriers.
• the LBT counter N is maintained independently on each carrier (sub-channel #1 and sub-channel #2); Upon the LBT counter N being equal to zero in one of the carriers (sub-channel #1) and the UE being able to initiate transmission on the corresponding carrier; The UE checks the channel status (e.g. whether the carrier was sensed idle or busy in the last CCA slot) and the LBT counter N on the other carriers (sub-channel #2).
• the UE Based on the channel status and status of the LBT procedure in the additional carriers (sub-channel #2), including the value of the LBT counter N, the UE evaluates whether channel access on at least one of the additional carriers (sub-channel #2) could be successfully completed within the packet delay budget.
• the UE defers data transmission on the carrier where the LBT was successful (sub-channel #1) until the next transmission opportunity
• the UE starts transmission on the carrier(s) where LBT was successful (sub channel #1).
• the UE may evaluate again as to whether channel access on at least one of the additional carriers (sub-channel #2) could be successfully completed within the packet delay budget.
• the UE defers data transmission on the carrier where the LBT was successful (sub-channel #1) until the next transmission opportunity
• the UE starts transmission on the carrier(s) where LBT was successful (sub channel #1).
• step S10 the UE starts Cat4 LBT procedure on multiple sub-channels and proceeds to scan the multiple channels, including where appropriate using self deferral (S20) until: the LBT procedure is successful on at least one sub-channel (Ci), that is a valid UL transmission opportunity is found (D5 yes) and when the UE is ready to transmit on at least one carrier (D15 - yes), then firstly the UE determines if there is any other sub-channel that could be used for transmission but where the LBT procedure is yet not successful (D25).
• S20 self deferral
• the UE initiates transmission on the available sub-channel(s) at step S30. If yes, the UE checks at D35 whether the channel status is IDLE on at least one of the additional sub-channels (Cj, j1i)
• a sub-channel is determined to be IDLE if the sub- channel was sensed as IDLE during the last CCA (clear channel assessment) measurement
• the sub-channel can be determined as IDLE also if the sub-channel was sensed as BUSY during the last CCA measurement, if e.g. the UE can estimate (based on past measurement samples) that the channel will become IDLE within a certain number of CCA slots.
• the sub-channel can be determined as BUSY even if the sub-channel was sensed as IDLE during the last CCA measurement, if e.g. the UE can estimate (based on past measurement samples) that the channel will become BUSY within a certain number of CCA slots.
• the UE initiates transmission on the sub-channel(s) that are available at step S30.
• the packet delay budget is defined as the maximum number of UL CG transmission occasions, K, for which a UE can defer data transmission on a sub channel with successful LBT.
• the next UL Tx opportunity is NOT within the packet budget delay if e.g. the UE was first ready to transmit on any of the available sub-channels at UL transmission opportunity #n, and the next UL transmission opportunity #n+K+i
• the UE checks the value of the LBT counter and the status of LBT (e.g. whether the UE is in additional defer mode - D55) on the corresponding sub- channel(s) and estimates the minimum time before the UE can complete successful cat4 procedure at steps S40 and S50 depending where UE is in the deferral period.
• the UE defers transmission until the next UL transmission opportunity and proceeds to scan the other channels by returning to step S20. Otherwise the UE initiates transmission on the available sub-channel(s) at step S30.
• Fig.5 shows the timings of the transmission according to an embodiment where interference is experienced and where there is no interference.
• the UE determines that the LBT counter of sub channel #2 is set to 10 and that the channel is currently busy and in this case determines from this that it is unlikely that the sub channel #2 will become available and have a transmission opportunity in the packet delay budget for the UE and thus it transmits a signal on subchannel #1 at the first available transmission opportunity.
• the UE determines the LBT counter in subchannel #2 is at 8 and that the channel is idle and it determines that the channel is likely to have a transmission opportunity within the packet delay budget and thus, it defers transmission on sub channel #1 until sub channel #2 is available and the two channels are used to transmit signals together.
• the advantages of the proposed channel access method as compared to prior art solutions is illustrated in Fig. 5.
• the proposed method combines the advantages of type A2 channel access (synchronized channel access in case of no or limited interference on one of the channels) with those of type At without self-deferral (fast channel access in case of interference on one of the channels).
• Fig.6 illustrates an apparatus or node according to an embodiment.
• the apparatus 10 is configured to transmit and receive signals on multiple channels within the unlicensed spectrum, shown schematically as double sided arrow 22, and may for example be a user equipment or a gNB.
• Apparatus 10 comprises transmit circuitry 30 and receive circuitry 32 which are configured to transmit and receive signals on multiple channels of the unlicensed spectrum via antenna 20.
• the apparatus 10 comprises scanning circuitry 40 configured to scan the multiple channels in the unlicensed spectrum using a listen before talk procedure to determine whether they are available. In other embodiments other scanning circuitry that uses other scanning procedures such as a clear channel assessment may be used.
• Apparatus 10 comprises control circuitry 50 that is configured to control the transmit, receive and scanning circuitry 30, 32, 40 to perform a method such as that illustrated in fig. 4 whereby the apparatus transmits signals, perhaps duplicate signals towards at last one further node on one or more channels within the unlicensed spectrum.
• the apparatus scans multiple channels in unlicensed spectrum to determine at least one channel that is available. On detecting an available channel and prior to transmitting a signal on that channel it determines whether another of the multiple scanned channels is likely to become available within a predetermined packet delay budget. Where not, then it transmits a signal at the first transmitting opportunity. Where so, then it waits for the next transmitting opportunity while continuing to scan the other channels and then makes the same assessment again.
• the packet delay budget may be set for a particular device, type of communication, or channel. It may be set centrally by the network or may be user equipment specific. It may be set as a time value, or as a counter value, the counter value may indicate a number of transmission opportunities.
• the network node may be configured to transmit the packet delay budget or deferral allowance to a user equipment.
• the network node may also transmit an indication that data duplication is to be used and/or a type of listen before talk that is to be used.
• the user equipment may comprise means configured to receive the deferral allowance signal and in response to set the deferral allowance accordingly. It may be set for a given set of uplink configured grants and could be configurable by a network node.
• the determination as to whether to defer transmission and as to whether or not a further channel is likely to become available in the packet delay budget may also be configurable and may depend on the current value of the LBT counter, the current availability, the historical availability and current channel loading and/or occupancy.
• program storage devices e.g., digital data storage media, which are machine or computer readable and encode machine- executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods.
• the program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media.
• the embodiments are also intended to cover computers programmed to perform said steps of the above-described methods.

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• 2020
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